This section is from the book "Mission Furniture: How To Make It", by Henry Haven Windsor. Also available from Amazon: Mission Furniture: How to Make It.
An easy and at the same time a good way to stain oak in imitation of the fumed effect, is to boil catechu in the proportion of 1/4 lb. to 6 lb. of water, after which cool and strain. Apply this to the wood, and when dry treat with a solution of bichromate of potash in the same proportion as with the catechu. Bichromate of potash alone in water will give a good stain. A solution of 2 oz. of pearl ash and 2 oz. of potash mixed in a quart of water makes a good stain. Potash solution darkens the wood, and when applied very strong will produce an almost ebon hue, due to what we might describe as the burning of the wood fiber.